You've heard of direct-to-DVD, so why not direct-to-comic-book? This collected volume of issues 1-5 of Buffy the Vampire Slayer Season Eight
is the official 8th season of the Emmy-winning TV series, written by
show creator Joss Whedon and packed with every surviving character from
the series (plus a few that you thought didn't make it). Only Angel and
Faith fail to make an appearance, both of whom show up later on (Angel
in his own after-the-series comic and Faith in the latter half of
season 8).
On the more meta side, I'd just like to say that this is an idea whose time has come. There's no good reason not to spin a TV show off into a comic once new seasons are no longer practical (due to viewership, actor availability or what have you). It's much cheaper, so the audience size is not an issue, and I think Season 8 really demonstrates that a comic book that is not only canon, but considered a part of the core continuity of the series will find its market.
Read on for the specifics (with no serious spoilers).

